Pistol Caliber AR Build

[Rastus]

Well, you guys may be on the way of convincing me there is a place in the world for a 300 blk.

[Big Frank]

With heavy subsonic bullets the 300 BLK has pistol-like muzzle energy, but the bullets are more aerodynamic and retain more of that energy as you get farther away.

[Rastus]

OK.  The Macon Armory has both direct impingement and blowback...what up with that other than how it cycles?  Is it just that with the direct impingement you can use existing lowers?  The price on direct impingement is way higher than what a lower costs these days.  These things must have been built and priced back in the Obama days when I could get $2k for a Bushmaster with 5,000 rounds through it.

[les snyder]

Rastus... any of the locked breech AR9s, like the CMMG Guard with a radially unlocking  bolt, the SiG MPX with the short piston or any DI that unlocks the bolt shoots considerably softer than the blow back...naturally the catch is that they are much more expensive...  most of the blow back 9mm use a bolt and buffer combination of about 21oz... gamers like myself limit the overall travel so that the bolt just clears the bolt hold open by 1/4" or so to limit the force exerted under recoil, and try to tune the buffer/spring with the ammunition... I shoot a 135 Bayou coated bullet with WSF that makes 130 power factor out of my G34, and about 146 out of the 16" carbine.. additionally, I use a hydraulic buffer... I found that the Enidine buffer greatly improves hit quality, more than reducing the dot movement

if I were to recommend an inexpensive  blow back AR9, I'd look at Palmetto State Armory's forged lower, Glock format (as the cartridges strip off the magazine directly into the chamber)... you may want to fool with a 5oz or so buffer when you decide on what ammunition...  their Gen4 bolt has a much preferable AR style extractor

for a non AR, about the only one I've shot is the CZ and did not like the ergonomics as it was "different" from all the AR's I shoot... I put a couple of rounds through a Beretta Storm, and early Marlin Camp rifle, but have not shot one of the new Ruger PC yet... the Ruger is I believe, a few bucks cheaper than the AR9s, but the AR platform is what I know something about, and over the years have acquired some specialty tools,  triggers, comps, hand guards for them

after the Steel Challenge match, I pirated the Vortex Venom from the .22lr and it now is on the AR9, and a new Venom and YHM riser is on order

[Pathfinder]

I have been considering a pistol caliber AR thinking about 10mm. I have heard that it is a "hot" caliber in a standard pistol, and I was considering that the AR platform may make it more manageable but still retain the power of the 10mm.

Now you have me thinking about a short-barrelled .300BLK instead. Truth be told, I already had a .300BLK pistol in the works - interrupted by a wee move to GA. It avoids the whole new receivers issue and as Kenny just found out, they are pricey!

[Sponsor]

[les snyder]

I had a piece of "stepped sidewall" brass case rupture in my 9mm, even with a relatively light load... I think a .300BLK shot in a locked breech carbine would be a whole lot safer choice than a blow back 10mm... even though .300BLK it is pricey to shoot

for USPSA,  most of the local shooters leave the 9mm brass on the ground to help speed up the squad... I buy it by the pound

[PegLeg45]

Just for the record, as it applies to my point of view on topics such as this: I don't do the match shooting game any more so my opinion is always skewed toward either defense, plinking, or hunting.


I guess it would boil down to intended use between a pistol caliber and the .300BLK.
If you use it for matches, the pistol ammo for practice and matches would be favorable due to cost.
If the intended use is self/home defense then it might be a wash...or possibly cheaper (or at least equal) for 20 rounds of Hornady .300 rifle ammo than for Hornady defensive ammo (I just paid $23 for a 20rd box). You still have to buy practice ammo for a defensive gun, but probably not as much as a match gun.
Reloading ammo might change the numbers some.

[Big Frank]

If you want the softest shooting 10mm carbine and don't care if it's an AR or not there's the Kriss Vector. At an even 8 pounds it's not the lightest, but if you're not carrying it a lot that may not matter. They come in 5 different colors if that makes any difference. They're coming out with a mag extension adds 18 rounds to the capacity of a G20 magazine, for a total of 33 rounds. I read elsewhere that you can expect 900 ft/lbs from a 16" barrel. That's roughly double the ME of a 300 BLK subsonic but only 2/3 the ME of a supersonic 300 BLK.

https://kriss-usa.com/14-rifles/carbines/80-kriss-vector-gen-ii-crb-flat-dark-earth-kv10-cfd20

[les snyder]

Sunday... first match with the Vortex Venom on the AR9... really opened up the field of view... need to check the hold over for close targets... regards

[Rastus]

The Venom looks to be a similar "format" as the EOTech.  If that's true, yes you should have a more open field of view and be quicker on target for targets within 15-25 yards....if it's like an EOTech. 

I don't get a good sense of the size of the Venom....how does the size of the sight compare to the EOTech?  It sure looks like it's a lot less bulky.

Thanks guys for the feedback.  I've been away working and am still in West Texas....dang it.  Not bad to visit but after a week it gets old coughing up caliche' dust.  I'm probably not going to do the Kriss Vector...I want the AR pattern so I don't my wife doesn't have to learn controls again.  So right now, I'm sitting on the fence on whether to go with the 10MM or 300 BLK and I wouldn't be there but except I haven't had time to ferret out ballistics and such.